1. Field of the Invention
The present invention relates to a model animal causing the white hair development, a method for establishing a model animal causing the white hair development, a method for successively growing a model animal causing the white hair development, a method for making research works about the white hair development, a screening method of means for controlling the white hair development, and a composition for controlling the white hair development.
More specifically, the invention relates to those described below:
(a) a model animal with a phenotype such that the color of the hair first growing after birth is black or almost black but the model animal causes the spontaneous onset of white hair development following aging;
(b) a method for establishing the model animal by a combination of a specific genetic manipulation procedure and a mating;
(c) a method for successively growing the model animal by mating together the resulting model animal to obtain a progeny of the model animal, which progeny has the same phenotype as that of the model animal;
(d) a method for making research works about the white hair development by utilizing such model animal;
(e) a method for screening for means for controlling the onset of white hair development (means for preventing/suppressing or promoting the white hair development), where the screening procedure is carried out as a part of such research works; and
(f) a composition for controlling the onset of white hair development, which composition contains a substance preventing/suppressing or promoting the white hair development as the component for controlling the white hair development, where the substance preventing/suppressing or promoting the white hair development is obtained by the screening.
2. Description of the Related Arts
In recent years, progresses have been made in the technique for preparing transgenic animals with extraneous functional genes introduced therein and in the genetic targeting technique utilizing homologous recombination of genes in ES cells and the like. Owing to these techniques, then, various model animals have been proposed, by which various human diseases and the like can be simulated for experiments and research works.
Generally, model animals for such purposes are preferably mammalian animals biologically close to humans. In particular, small mammalian animals typically including rodents such as mouse and rat are relatively readily available and usable, so these small mammalian animals are the most suitable in view of their rapid growth and their rapid alterations of generations.
[Literature 1] Official Gazette of JP-A-9-131146
[Literature 2] Official Gazette of JP-A-2001-231402
The Literature 1 and the Literature 2 disclose examples of such animals. Specifically, the Literature 1 discloses a transgenic rat with the impairment of sperm generation because of the introduction of the c-myc gene therein under the control of the metallothionein IIA promoter. The Literature 2 discloses a model rat causing the onset of prostate cancer, where a transgene prepared by conjugating the gene of the SV40 large T antigen to the downstream of the rat probacin gene promoter was introduced. As described above, the model animals proposed in the related art are overwhelmingly animals in relation with serious human diseases such as cancer and diabetes mellitus.
Alternatively, a field exists for aesthetic problems or problems about outward appearances in no relation with human health or death, but the fundamental causes or countermeasures of the problems have not yet been elucidated. Nonetheless, a large market of related products so as to overcome or avoid those problems is generated. A typical example thereof is the problem of white hair development following aging of humans with dark-colored hairs such as black hair and brown hair.
Specifically, a great number of people are bothered with the white hair development following aging in view of aesthetics and appearance. Therefore, hair dyes are now making a large market. However, hair dying is only a simple appearance modification so dying should be repeated when hair grows only at a low level. Because dying requires laborious works every time of hair growing, hair dying does not sufficiently satisfy users.
For example, pharmaceutical products expressing an effect of preventing white hair development or food products commonly considered effective for preventing white hair development are found in general. Since the mechanism of the white hair development has not yet been elucidated, however, the effects of these pharmaceutical products or food products lack scientific grounds. Furthermore, persons continuously incorporating these pharmaceutical products and food products have diverse genetic dispositions and have very diverse dietary life styles in so diverse environments. Thus, it is hard to observe any statistic or empirical reliability in the effects of these pharmaceutical products and food products.
An effective experimental means for making research works about the mechanism of the white hair development in humans when provided will make a dramatic progress in the research works and development of the white hair development and means for controlling the white hair development (means for preventing/suppressing or promoting the white hair development). Any model animal preferable from the standpoint of the white hair development following aging, of which the color of the hair first growing after birth is black or almost black, would potentially be the effective experimental means. However, such model animal has not yet been provided or proposed actually.